1. Field of the Invention
The present invention relates to an electron emitter elements, their use and fabrication processes therefor. More particularly, the invention relates to an electron emitter elements, their use and a fabrication processes therefor which ensure excellent display characteristics (high brightness, high resolution, high response time, low power consumption and wide view angle). The electron emitter element of the present invention is a promising electron source for a thin panel display device in wide application fields such as of portable terminals and wall-type TVs.
2. Description of Related Arts
Electron emitter elements are capable of extracting electrons from emitter tips on an emitter electrode by applying a voltage between the emitter tips and a gate electrode for electron extraction. The emitter tips are formed on the emitter electrode by way of semiconductor microprocessing techniques. The micron-order size of the emitter tips permits highly dense integration of the electron emitter elements.
FIG. 17 and FIG. 17a show one exemplary construction of a thin flat panel display device employing electron emitter elements. The display device includes a cathode plate and an anode plate facing opposite to each other across a vacuum space. Pixels each comprising a plurality of electron emitter elements are arranged in a matrix on the cathode plate. Emitter electrode lines (layers) 103 of the respective electron emitter elements intersect gate electrode lines (layers) 110 on an insulating (glass) substrate 101. An insulating film 104 is interposed between the emitter electrode lines 103 and the gate electrode lines 110. Several hundred to several thousand gate openings are formed in each of the intersection areas of the electrode lines 103 and 110, and emitter tips 108 are formed within the respective gate openings in contact with a corresponding emitter electrode line to define each pixel 111. Since the electron emission characteristics of the emitter tips 108 are nonlinear, the emitter tips 108 can be individually driven by selectively actuating the emitter electrode lines 103 and the gate electrode lines 110. Electrons extracted from emitter tips in a selected pixel 110 on the cathode plate 112 reach the anode plate 114 applied with a fluorescent substance 113 so that the fluorescent substance 113 is excited to emit light, which is used for display.
FIGS. 18(a) to 18(h) are schematic diagrams illustrating the respective steps of a conventional process for fms illustrating the respective steps of a conventional process for fabricating electron emitter array by vacuum evaporation. An emitter electrode material 102 is deposited on an insulating substrate 101 to form a plain film (see FIG. 18(a)). The plan film of the emitter electrode material 102 is patterned to form striped emitter electrode lines 103 (see FIG. 18(b)). Thereafter, an insulating film 104 is formed on the insulating substrate 101, and then a gate electrode made material 105 is deposited thereon (see FIG. 18(c)). In turn, the insulating film 104 and the gate electrode material 105 are etched to form a plurality of cylindrical gate openings 106. Thus, parts of emitter electrode are exposed in the gate openings 106 (see FIG. 18(d)). Then, aluminum or a like material is obliquely deposited on the resulting insulating substrate 101 to form a sacrificial film 107 in such a manner that the material is not deposited on the bottom of the gate openings 106 (see FIG. 18(e)). Further, an emitter tip material 108 such as molybdenum is vertically deposited on the resulting insulating substrate 101. As the emitter tip material 108 is deposited on the emitter electrodes, the gate openings 106 are gradually covered with the emitter tip material 108. When the gate openings 106 are completely covered, conical emitter tips 109 are formed on the emitter electrodes within the gate openings 106 (see FIG. 18(f)). In turn, the emitter tip material 108 deposited in a region other than around the gate openings 106 is removed by etching to expose the sacrificial film 107 (see FIG. 18(g)). Then, the resulting insulating substrate 101 is dipped in an aqueous solution of phosphoric acid for dissolution of the sacrificial film 107, so that the remaining emitter tip material 108 around the gate openings 106 is lifted off and the emitter tips 109 are exposed in the gate openings 106. Finally, a gate electrode material 105 is deposited on the resulting insulating substrate 101, and then patterned to form striped gate electrode lines 110 which extend perpendicular to the emitter electrode lines. Thus, an electron emitter array of a matrix structure is provided which is formed with emitter tips in intersection areas of the emitter electrode lines and the gate electrode lines (see FIG. 18(h)).
Thus, the formation of the plurality of electron emitter elements on the single substrate requires a plurality of process steps and inevitably entails dust contamination, which results in a defect. Particularly, when a defect occurs due to a short circuit between an emitter electrode line and a gate electrode line in one electron emitter element, it becomes impossible to apply a voltage to electron emitter elements connected to the same electrode lines as connected to the defective electron emitter element so that these electrode lines become defective. Further, the electron emission characteristics are sensitive to the surface conditions of the emitter tips. Therefore, the electron emission characteristics are more influenced by the dust contamination with the increase in the number of process steps, resulting in a reduced yield. In addition, a greater number of process steps increases the production cost.
Furthermore, when a pin hole is produced in the insulating film interposed between the emitter electrode lines and the gate electrode lines in crossover portions therebetween, the pin hole causes a short circuit between the gate electrode lines and the emitter electrode lines to interfere with the operation of the electron emitter array.